Winter storms, high tides, and saturated ground can flood streets, homes, and roads across San Mateo County. OneShoreline works with cities, the County, and regional partners to help residents and businesses prepare early, understand local conditions, and find trusted information.

• Find your sandbag site and city public works contacts
• Sign up for SMC Alert emergency alerts
• Download the Household and Renter Flood Checklist (PDF)

October is Flood Preparedness Week in California. It's a good time to take the steps below before the first big storm.

Start Here: Three Actions to Take Now

Know Your Risk

Learn whether your home, workplace, school, or regular routes could flood from the Bay, the ocean, creeks, or overloaded storm drains. Look up your address on the FEMA Flood Map Service Center.

Prepare Your Home and Plans

Clear drains where it's safe to do so, protect important belongings, photograph your property, check your insurance, and plan other routes in case roads close. Start with the Household and Renter Checklist below.

Stay Informed

Sign up for SMC Alert to get warnings for your address by text, phone call, and email. Look up your evacuation zone and download the app at Genasys Protect. If you get Nixle messages from your city or police department, sign up for SMC Alert too; the two systems are separate.

Find Flood Resources in Your Community

Cities, the County, and other agencies provide flood services and emergency information. Start with your city's public works department, or with the County if you live in an unincorporated area.

• Sandbags: The San Mateo County sandbag list shows this season's sites, hours, and public works phone numbers for each city and for unincorporated areas. Many sites ask you to call ahead, and some serve residents only.
• County winter weather information: San Mateo County Winter Weather Preparedness
• Road conditions and closures: Caltrans QuickMap
• Report flooding or a clogged storm drain: Call your city's public works department. You'll find the number on the sandbag list.
• Neighborhood example: Belle Air Neighborhood Storm Season Safety Flyer for San Bruno households (English, Spanish)

In an emergency, or if anyone's life is in danger, call 911. Sandbag supplies and site hours can change during a storm, so check with the agency before you go.

Household and Renter Checklist

Get ready before winter and to stay safe during storms.

To read this page in another language, use the translate button at the top of the page. Automatic translation may contain errors.

Before Winter

Start with the County's four steps:

1. Make a plan. Agree on where your household will meet, choose an out-of-area contact, know two ways out of your neighborhood, and look up your evacuation zone at Genasys Protect. For planning help, visit Ready.gov: Make a Plan.
2. Build a kit. Gather water, food, medications, chargers, and copies of important documents to last 3 days. Use the Ready.gov kit checklist, or build supplies over time with the County's 12-week Preparedness Calendar (available in multiple languages).
3. Find your sandbag site on the County sandbag list before the first storm.
4. Sign up for SMC Alert, or update your address and phone if you've moved.

Then:

• Find out whether your home or regular routes have flooded before.
• Clear leaves from gutters, downspouts, and the storm drain nearest your home. Use a rake, and never lift a grate.
• Move important documents and valuables above the level water could reach.
• Photograph your home and belongings so you can document them for insurance.
• Check your flood coverage. Most home and renters policies don't cover flooding, and new flood policies usually take 30 days to start. Learn more at FloodSmart and United Policyholders.
• Plan for pets, medications, mobility needs, and power outages.

Before and During a Storm

• Watch National Weather Service forecasts and local alerts.
• Move vehicles out of low-lying areas when officials advise.
• Stay away from flooded roads, trails, underpasses, and shorelines.
• Don't drive or walk into flood water.
• Report flooding to your city's public works department.
• Follow evacuation and safety instructions from emergency officials.

Tips for Renters

• Ask your property owner or manager whether the building has flooded before and what they plan to do in a storm.
• Know how to report drainage or building problems.
• Consider renters insurance, and check what it covers. Most renters policies don't cover flood damage.
• Keep essential documents, medications, and electronics where you can grab them quickly.

Flood Protection Supplies and How to Choose Them

Flood protection supplies can keep water out of your home, manage water that gets in, and protect people and belongings.

You can reduce flood risk at home in many ways, from simple steps like raising appliances and important documents to tools such as flood barriers, pumps, and drainage improvements. The right supplies and setup depend on how flooding happens, the layout of your home, and your household's needs.

Choose Supplies That Fit Your Home

Not sure where to start? OneShoreline and our partners created the Flood Supplies Decision Guide (English / Spanish) to help households choose flood protection options that fit their situation.

The guide helps you identify your flood concern, such as where water comes from or what parts of your home get wet, and walks through common flood protection options. It explains what each tool does, how much setup it takes, and which approaches may work best for your home.

Business and Property Checklist

A few inches of water or a few days without power can cost businesses and property owners stock, equipment, and customers. Before the first storm, plan:

• How you'll reach staff and customers before, during, and after a storm
• When and how you'll close and reopen
• How you'll protect inventory, equipment, and records
• What you'll do if vendors or deliveries can't reach you
• How staff and customers will get in if your usual route floods
• What your insurance covers, with photos of your property and equipment
• How tenants and property owners will coordinate on drainage, repairs, and access

When a Storm Is Approaching

Monitor

• National Weather Service forecasts and warnings
• SMC Alert and other local alerts
• City and County updates
• Road and transit conditions on Caltrans QuickMap

Act

• Charge phones and gather essential supplies.
• Move vehicles and belongings out of low areas if needed.
• Stay away from low-lying roads and the shoreline.
• Use sandbags only where it's appropriate and safe.
• Follow instructions from local emergency officials.

Stay Out of Flood Water

Never drive, bike, or walk into flood water. 6 inches of moving water can knock you off your feet, and 12 inches can carry away most cars.

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Sandbag supplies, site hours, road conditions, and other details can change quickly during storms. Always confirm with the responsible agency. This page shares general preparedness information and doesn't replace instructions from emergency officials.

To read this page in another language, use the translate button at the top of the page. Automatic translation may contain errors.